Switch for series dynamo-electric machines



(No Model.)

C. R. ARNOLD. SWITCH FOR SERIES DYNAMO ELECTRIC MACHINES.

No. 460,245. Patentfad Sept. 29, 1891.

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, MM@ may Ran/wm Tlf-77% v UNITED STATES PATENT OFFICE.

CRAIG RITGHIE ARNOLD, OF SHARON HILL, PENNSYLVANIA.

SWITCH FOR SERIES DYNAMO-ELECTRIC MACHINES.

SECIFICATION forming part of Letters Patent No. 460,245, dated September29, 1891.

Application filed November l0, 1890. Serial No. 370,937. (No model.)

To all whom it may concern:

Be it known that I, CRAIG Rrrcnin An- NOLD, a citizen of the UnitedStates, and a resident of Sharon Hill, in the county of Delaware andState of Pennsylvania, have invented certain new and useful Switches forSeries Dynamo-Electric Machines, of which the following is aspecification.

My invention relates to means for throwing out of operation that classof dynamo-electric machines in which the field-coil and the armature arein series with one another and with the work.

The object of my invention is to provide a switch whereby the machinemay be connected to and disconnected from its working circuit withoutinjury to the switch-contacts and without danger of damaging thearmature or field-magnet coils of the machine.

It has heretofore been proposed to throw a series dynamo-machine out ofaction by forming a shunt for the armature-current around thefield-magnet coils and the series circuit, the effect being tosubstantially put the armature on short circuit while the held-magnetwas losing its power. This is in practice objectionable, because thewhole armaturecurrent can iiow on short circuit, and as it takes timefor the field to discharge the machine is practically for a time runningon short circuit. In this method of throwing the machine out ofoperation the switch-contacts of the switch, which nally open thecircuit of the armature, are also liable to great damage.

My invention consists, essentially, in the combination, with aseries-wound dynamoelectric machine, of a circuit opening and breakingswitch therefor having a supplemental contact placed in the path of theswitch between the circuit-closing and circuit-breaking position andconnected directly to one terminal of the field-magnet coil of themachine and adapted to be engaged by the switch as it passes tocircuit-breaking position and before it leaves its normal position otclosure of circuit, all as hereinafter described, whereby in operatingthe switch a shunt around the field-magnet coils is completed for thecurrent which flows from the armature over the line.

In the accompanying drawings I have illustrated my inventiondiagrammatically, A being the series field-coil of a dynamo-electricmachine, which is traversed by the current from the armature B. Theworking circuit containing the translating` devices, such aselectric-arc lamps, (indicated at G,) is fed by the current which flowsin series through the armature and field.

E indicates a suitable switch-lever, and G the normal contact therefor,whereby the circuit of thc armature B is completed through thefield-magnet A, a series of lights or other translating devices C, andback to the armature. lVhen the switch-lever is in position upon itsnormal contact G, the machine operates as a series dynamo-machine inobvious manner.

I is a non-conducting plate or rest upon which the lever F. may bearwhen itis thrown over to open the circuit ofthe machine, or, in otherwords, to disconnect the same from the line, and K is a suitablestop-pin for arresting the movement of the circuit-opening lever when itis thrown to disconnect the machine from line and throw it out ofaction.

F indicates a supplemental contact with which the switch engages andmakes contact as it passes from position in contact with G to thecircuit-openin g position. The distance between the plates G F is madeso small or the width of the contact portion of the switchlever so largethat an electrical connection will be formed and maintained for aninstant between G and F as the lever is thrown to open the circuit. Thecontact F is connected by a wire, as D, directly with one terminal ofthe field-magnet coil A, the other contact G being connected to theopposite terminal. W'hen the switch is closed upon contact G, thecircuit of the dynamo is complete through the working circuit in theordinary way, the current generated by the armature acting to generateand maintain the magnetic field in which the armature revolves.

As the switch is moved to open the circuit or throw the machine out ofaction and disconnect it from line after the manner of the usualline-switches, contact will first be made with F, connection beingmaintained with G for the time being, so that the current ofthe IOOarmature instead of iiowing through the iield A may flow through thebranch around the same and over the working circuit through the workingresistance C. Current being now shunted from the iield A, the lattergradually loses its power and the electro-motive force developed by thearmature falls; but during thc fallof the field-magnetism no damage canensue, because the current of the armature forms circuit only throughthe resistance interposed between the terminals by the working circuit.The machine therefore dies down withoutdamage to a point where itdevelops an inappreciable or practically ineffective current due only tosuch fmal residual magnetism as maybe left in the field-magnet core. Theoperation may now be completed by throwing the switch full tocircuit-openin g position, so as to not only throw the machine out otaction, but to disconnect it from the circuit. In this action the leverfirst breaks contact with G; but as the machine is now practically deadno injurious dashing will occur at such contact and the final breakageof the circuit of the machine at F, which coinpletes the throwing of thecircuit of the machine out of operative condition, and the disconnectionot the apparatus from line in the ordinary way will be accomplishedwithout any damage.

Vhile I have described the operation as if there was a pause ofconsiderable duration after the closure of the contact or connectionfrom F to G, it will be understood that in practice the switch will bemoved directly from one to the other, but that the interval during whichthe circuit is completed between F and G will be sufiicient to cover thetime during' which the magnetism of the field will fall to such anextent that no large orinj urious Hash or spark will occu r when theswitchlever finally leaves the contact G to rest fully or only upon thecontact F.

Vhat I claim as my invention isl. The combination, with a series-wounddynamo-electric machine, of a circuit making and breaking switch forthrowing' the machine out of action and disconnecting it from the line,as described, having a contact, as G, through which the series circuitof the armature-field and translating devices is completed in series,said contact G being connected directly to one terminal of theiield-magnet coil of the machine, and a supplemental contact, as F,connected directly to the opposite terminal of the field-magnet coil andplaced in position to be engaged by the switch in passing from positiono t circuit closed to circuit broken and before it leaves the contact G.

2. The combination, with a series-wound dynamo-electric machine, of astarting and stopping circuit-breaking switch placed in the seriescircuit of the armature and field and connected directly to line, andtwo contacts for said switch, one connected directly to a terminal ofthe field-magnet coil and forming' the norm al contact of the switch andthe other connected directly to an opposite terminal ol' said coil at apoint between said field-coil and the armature of the machine andarranged to be engaged by the switch as it passes from circuit-closingposition to circuit-opening position, or position to disconnect thcapparatus from the line.

Signed at Chester, in the county of Delaware and Stare of Pennsylvania,this 25th day of October, A. D. 1890.

CRAIG RI'lCl'IIE ARNOLD.

Witnesses:

Conn M. HiNKsoN, J. WALTER LiNDsAv.

